1. Field of the Invention
The present invention relates to a semiconductor device substrate, and a method of manufacturing the substrate and a semiconductor device.
2. Description of the Related Art
Semiconductor devices are increasingly reduced in size and weight. With a smaller thickness of portable devices in recent years, a smaller thickness is also required in semiconductor devices used therefor.
As a method of manufacturing a thin semiconductor device, a method as illustrated in FIG. 2A to FIG. 2C is conventionally employed using a substrate shown in FIG. 1A and FIG. 1B.
FIG. 1A is a top view of the substrate, and FIG. 1B and FIG. 2A to FIG. 2C are section views of the substrate taken along the C-Cxe2x80x2 line in FIG. 1A for illustrating manufacturing steps.
As shown in FIG. 1A, substrate 1 is formed of alumina ceramic and is provided with a plurality of externally guiding electrodes 2 at regular intervals. As shown in FIG. 1B, each of externally guiding electrodes 2 is configured to comprise element connecting electrode 2a, via hole 2b, and external device connecting electrode 2c such that element connecting electrode 2a on the surface is electrically connected to external device connecting electrode 2c on the back surface thorough via hole 2b. 
As shown in FIG. 2A to FIG. 2C, each semiconductor device is formed by holding substrate 1 as shown in FIG. 2A to dispose and fix semiconductor element 3 onto element connecting electrode 2a with a conductive paste, an AuSn alloy, an AuSi alloy or the like, electrically connecting an electrode of fixed semiconductor element 3 to element connecting electrode 2a with wire 4 formed of gold, aluminum or the like, applying and curing liquid resin 7 with printing or application through potting (FIG. 2B), bonding the surface of the substrate on which resin 7 is cured to a tape for dicing, and cutting the substrate at A-Axe2x80x2 planes by a dicing machine (FIG. 2C).
In the aforementioned method of manufacturing a semiconductor device, however, a reduced viscosity of resin 7 due to an increased temperature after the application thereof causes resin 7 to easily flow in the outer portions thereof, causing resin 7 to be spread without maintaining the shape at the application. As a result, the method has disadvantages that resin 7 applied at a small thickness leads to variations in thickness of applied resin 7 after the cure due to the flow of resin 7, and that semiconductor element 3 and wire 4 tend to be exposed in the portion of resin 7 with a smaller thickness.
In addition, since the alumina ceramic is used for the material of substrate 1, a smaller thickness of substrate 1 causes the concentration of mechanical stress and thermal stress in the outer portions of a substrate with many defects, easily producing cracking in the substrate.
Furthermore, since the linear expansion coefficient of a resin typically ranges from 1 to 4xc3x9710xe2x88x925 (/xc2x0 C.) which is greatly different from that of an alumina ceramic substrate at 0.6xc3x9710xe2x88x925 (/xc2x0 C.), cooling of resin 7 after the cure produces stress caused by the difference in the linear expansion coefficient between resin 7 and substrate 1 to readily generate a warp in the substrate. Such a warp of the substrate makes it difficult to entirely bond the adhesive tape for use in bonding to the resin applied surface of the substrate when the substrate is cut into individual semiconductor devices. Thus, disadvantages are present in which the substrate cannot be cut finely and chips are scattered from the cut product or the chips may damage and break the cutting teeth.
FIG. 3 illustrates a manufacturing method of another prior art presented in Japanese Patent Laid-open Publication No.10-294498.
The manufacturing method illustrated in FIG. 3 manufactures a semiconductor device by disposing and fixing semiconductor element 3 onto substrate 1, connecting an electrode of semiconductor element 3 to electrode 10 on substrate 1 with wire 4, attaching frame 9 formed of a fluororesin around the disposed electrodes, and applying and curing resin 7.
In such a prior art, the fluororesin is used as the material of the frame. However, its linear expansion coefficient ranges from 4 to 10xc3x9710xe2x88x925 (/xc2x0 C.) which is greatly different from that for an alumina ceramic substrate at 0.6xc3x9710xe2x88x925 (/xc2x0 C.), and stress is applied due to the difference in the linear expansion coefficient between frame 9 formed of the fluororesin and substrate 1.
Thus, the prior art has a disadvantage that a smaller thickness of the substrate for achieving a smaller size and a lighter weight causes a significant warp in substrate 1 due to changes in temperature after the cure of the resin, thereby impairing the adhesion between the resin surface of substrate 1 and the adhesive tape when the substrate is cut into semiconductor devices.
In addition, when frame 9 formed of the fluororesin is reduced in thickness to suppress the warp of the substrate, the resin near frame 9 formed of the fluororesin flows to readily produce variations in thickness of the resin.
FIG. 4 illustrates a semiconductor device and a manufacturing method thereof of another prior art presented in Japanese Patent Laid-open Publication No.10-150127.
The manufacturing method illustrated in FIG. 4 manufactures a semiconductor device by using substrate 1 including groove 11 formed therein, disposing semiconductor element 3 on substrate 1, connecting an electrode of disposed semiconductor element 3 to electrode 10 on substrate 1 with wire 4, and then applying and curing resin 7.
In such a prior art, groove 11 formed to stop the flow of the resin causes a smaller thickness of the substrate near groove 11 to reduce the strength of the substrate near groove 11, making it easy to produce cracking in the substrate.
An additional disadvantage is that since resin 7 near groove 11 flows toward groove 11, a difference in height readily occurs after the cure between the resin near groove 11 and the resin in the central portion to result in large variations in thickness of the resin.
FIG. 5 illustrates a method of manufacturing a semiconductor device of another prior art presented in Japanese Patent No.2867954.
The manufacturing method in FIG. 5 manufactures a semiconductor device by using a substrate including a plurality of recesses 12 in grid form in which a plurality of element connecting electrodes 2a are connected to external device connecting electrodes 2d via through holes 2e, respectively, disposing semiconductor element 3 within each of recesses 12 in the substrate, connecting semiconductor element 3 to element connecting electrode 2a with wire 4, applying and curing resin 7, and cutting the substrate.
Such a prior art has a disadvantage that, since recess 12 has a small area, each recess 12 is likely to contain foams at the application of resin 7 which may remain as foams in the resin portion of the semiconductor device after the cure of the resin, and that large variations tend to occur in thickness of the resin since the foams escape during the cure of the resin to reduce the thickness in those portions.
When each semiconductor device is cut at the A-Axe2x80x2 line in frame 1b, a certain width of the frame is required for the cutting, and accordingly, a smaller size of a semiconductor device is difficult to achieve.
When each semiconductor device is cut in the resin portion to avoid frame 1b (cutting at the B-Bxe2x80x2 line), the number of obtained products per substrate is reduced corresponding to frames 1b which occupy a large area in substrate 1, and additionally, many steps are required for the cutting, thereby making it difficult to reduce cost.
Furthermore, Japanese Patent Laid-open Publication No.11-67799 proposes, for xe2x80x9cproviding a method of manufacturing electronics capable of obtaining smoothness of a top surface and verticality and linearity of a side surface without loosing productivity and economy of a stencil printing and encapsulating technique,xe2x80x9d xe2x80x9cwhen many electronics elements mounted on a wiring substrate for obtaining a number of products are encapsulated in a resin, first forming a dam portion along the periphery of the element mounting surface of the wiring substrate by using a dam forming resin and applying stencil printing means, next, before or after the cure of the dam portion, forming a resin layer by applying the stencil printing means in the entire area surrounded by the dam portion for encapsulating the electronics elements in their entirety, and curing the uncured dam portion and the resin layer, and then cutting and dividing the wiring substrate and the resin layer into individual electronic elements.xe2x80x9d
It is an object of the present invention to provide a semiconductor device substrate, and a method of manufacturing the substrate and a semiconductor device which remove the disadvantages possessed by the aforementioned prior art manufacturing methods and support a reduction in size and weight.
The present invention employs a semiconductor device substrate and a method of manufacturing a semiconductor device configured as follows to achieve aforementioned object.
A semiconductor device substrate according to one aspect of the present invention comprises a plurality of externally guiding electrodes for guiding electrodes of mounted semiconductor elements to the outside, respectively, and disposed at regular intervals near the center of a base formed of alumina ceramic, glass epoxy or the like, wherein the substrate is configured such that a frame formed of the same material as the base is formed in the outermost portion of the base to surround the area in which the electrodes are disposed.
A semiconductor device substrate according to another aspect of the present invention comprises a substrate including a base formed of alumina ceramic, glass epoxy or the like, and a frame formed of the same material as the base and formed in the outermost portion of the base to surround an inner area of the base, and the semiconductor device substrate further comprises, on the substrate, externally guiding electrodes, each of the electrode comprising an element connecting electrode provided at regular intervals in an area surrounded by the frame, an external device connecting electrode provided at regular intervals on the back surface of the substrate, and a via hole connecting both of the electrodes, and a plurality of semiconductor elements disposed and fixed onto the area of the base surrounded by the frame and connected to the element connecting electrodes, respectively, wherein a thermosetting resin or a thermoplastic resin is applied and cured in the area surrounded by the frame at a thickness substantially the same as the height of the frame.
A method of manufacturing a semiconductor device substrate according to the present invention comprises the steps of disposing and fixing a semiconductor element onto the area of the base surrounded by the frame in the semiconductor device substrate configured as described above, connecting the semiconductor element to the element connecting electrode, applying a thermosetting resin or a thermoplastic resin in the area surrounded by the frame at a thickness substantially the same as the height of the frame, and curing the resin.
The method of manufacturing a semiconductor device substrate preferably comprises the step of removing foams within the resin between the step of applying the resin and the step of curing the resin. In addition, the method of manufacturing a semiconductor device preferably comprises the step of applying a sheet with a softening point higher than the temperature at which the resin is cured or the temperature at which the thermoplastic resin is melted through heating and then curing the sheet, and the step of stripping off the sheet after the cure, between the step of applying the resin and the step of curing the resin.
A method of manufacturing a semiconductor device according to the present invention uses a semiconductor device substrate comprising a substrate including a base formed of alumina ceramic, glass epoxy or the like and a frame formed of the same material as the base and formed in the outermost portion of the base to surround an inner area of the base, and externally guiding electrodes, each of the electrode comprising an element connecting electrode provided at regular intervals in an area surrounded by the frame, an external device connecting electrode provided at regular intervals on the back surface of the substrate, and a via hole connecting both of the electrodes, and the method comprises the steps of disposing and fixing a semiconductor element onto the area of the base surrounded by the frame, connecting the semiconductor element to the element connecting electrode, applying and curing a thermosetting resin or a thermoplastic resin in the area surrounded by the frame at a thickness substantially the same as the height of the frame, and cutting the semiconductor device substrate into individual semiconductor devices after the resin is cured.
In the method of manufacturing a semiconductor device, the step of curing the resin is preferably performed with a sheet applied onto the resin, the sheet having a softening point higher than the temperature at which the thermosetting resin is cured or the temperature at which the thermoplastic resin is melted through heating, and the step of cutting the semiconductor device substrate into individual semiconductor devices is preferably performed after the sheet is stripped off. In addition, the method of manufacturing a semiconductor device preferably comprises the step of removing foams within the resin between the step of applying the resin and the step of curing the resin. The method of manufacturing a semiconductor device preferably comprises the step of applying a sheet with a softening point higher than the temperature at which the resin is cured or the temperature at which the thermoplastic resin is melted through heating and then curing the sheet, and the step of stripping off the sheet after the cure, between the step of applying the resin and the step of curing the resin.
The above and other objects, features, and advantages of the present invention will become apparent from the following description based on the accompanying drawings which illustrate examples of preferred embodiments of the present invention.